1. Field of the Invention
The present invention relates to a ventilated rotor which is suitably used as a rotor for a disc brake of a vehicle, more specifically, relates to a ventilated rotor in which vibration characteristic is improved and so-called brake noise is reduced effectively.
2. Description of the Related Art
A rotor for a disc brake of a vehicle rotates together with a wheel and has a pair of opposed slide boards which respectively form friction surfaces together with corresponding one of a pair of brake pads. When the brake pads are respectively brought into contact with corresponding one of the slide boards and they slide, the wheel is braked and its rotation is stopped.
An example of such a rotor for the disk brake is a ventilated rotor.
This ventilated rotor improves a cooling characteristic of the rotor by utilizing ventilation effect, and its resultant braking property reduces the effect of a friction heat. More specifically, the ventilated rotor is arranged so that a plurality of vent holes are formed between an inner circumference portion and outer circumference portion of the rotor.
Moreover, in the disc brake having such a ventilated rotor, it is one of important research and development items to reduce brake noise from a viewpoint of obtaining high product property.
Japanese Patent Application Laid-Open No. 58-200827 discloses a conventional ventilated rotor which is devised in order to reduce brake noise.
Particularly in FIGS. 1 and 2 of this publication, between cyclic slide boards which face each other and respectively form friction surfaces with corresponding one of brake pads, thirty cooling fins are provided, and the spaces between the cooling fins serve as vent holes. These cooling fins form six groups, each group composed of five cooling fins, and the intervals between the groups and between the cooling fins respectively have sizes of .theta.2, .theta.1, .theta.0, .theta.1 and .theta.2 (.theta.2&gt;.theta.1&gt;.theta.0) in order from the end, and widths of the cooling fins in each group are respectively a2, a1, a0, a1, and a2 (a2&gt;a1&gt;a0) in order from the end.
In such an arrangement, the ventilated rotor has a form such that the inner arrangement between the cyclic slide boards are repeated periodically six times in the circumferential direction, and as a result, this prevents a stationary vibration mode of a diameter node of multiples of 3 from occurring.
However, in such a conventional arrangement, the occurrence of a vibration mode of an arbitrary diameter node can be prevented theoretically, and thus the brake noises can be restrained, but in the case where this is applied to a vehicle practically, further improvement is desired.